Exposure control for photographic apparatus



Aug. 9, 1938. J. MIHALYI 2,126,338

EXPOSURE CONTROL FOR PHOTOGRAPHIC APPARATUS Filed March 25, 1956 8 I I I 6 g 1 7 .9

FUSE

o v 31 j m 32 INVENTOR. Joseph Mlhalyl 3 BY ATTORNEYS Patented Aug. 9, 1938 PATENT OFFICE I EXPOSURE CONTROL FOR PHOTOGRAPHIC APPARATUS Joseph Mihalyi, Rochester, N. Y., assignor, by

mesne assignments, to Eastman Kodak Company, Jersey City, N. J., a corporation of New Jersey Application March 23, 1936, Serial No. 70,320

ZCIaims.

This invention relates to'exposure controls for photographic cameras, and is particularly directed toward providing means whereby the photographic light value of an object or scene toward which a camera is directed activates a light sensitive device which translates this light value into a visual indication or reading, in combination with means for manually adjusting the camera exposure setting to a value determined by said indication, to accomplish correct exposure of the particular film or plate in the camera.

It has become quite common to employ obiectives of different focal lengths interchangeably on a single camera. This practice makes it desirable to alter or adjust the light measuring device so as to take into account the different exposures needed when different focal length ob jectives are used even though the same lighting conditions exist. When this adjustment is left to the operator it is frequently overlooked by him when he changes his objective with a consequent wastage of time and material or at least a result which is far from satisfactory.

This disadvantage is eliminated by my present invention by relieving the operator of the responsibility of making any adjustment upon changing from one focal length objective to another. This is accomplished by providing the objectives with means for assuring the correct adjustment when the objective is positioned on the camera.

This invention is applicable to cameras for either still or motion pictures, but for simplicity the drawing forming a part of this specification illustrates a preferred form of the invention as applied to a motion picture camera of a stand ardlzed type.

Referring to the drawing:

Fig. 1, is a fragmentary side elevation of a motion picture camera with the cover removed, and with the parts embodying this invention shown partly in section;

Fig. 2 is a section substantially on line 2--2 of Fig. l;

Fig. 3 is a front elevation; and

Fig. 4 is aperspective view looking toward the front of a camera.

It is one object of this invention to enable the operator of a camera to direct the latter .at the view or subject to be photographed, and while the view is visible in the finder, and the camera is in position for action, to adjust the exposure setting to the required value without having to remove his attention from the finder. This object is most conveniently attained by renderingthe scale which gives the light-value reading visible to the operator simultaneously with the view, and by providing a manual control, conveniently located, whereby the operator may adjust the exposure settings in accordance with said reading. The manual control preferably includes a separate indicator, also visible to the operator simultaneously with the view, which, when moved to a predetermined relation to the light-value scale reading, will inform the operator that the exposure device has been set to the required value. This latter condition is attained without diverting the attention of the operator from the finder.

In the particular embodiment illustrated here? in, a motion-picture camera I having the usual lens mount 2' with focusing bezel 2 and lens L projecting from its front is provided with a suitable operating release 3 and a cover look I. A compartment 4 within a shell or housing 5 which may be a part of the camera body is preferably located above the lens mount 2 and has a front opening 6 with a cover glass 1, directly back of which is a cellular baille B which limits the cone angle of the light incident on a light sensitive cell 9 positioned immediately behind the battle 8. This cell 9 which preferably is of the dry photo voltaic type is connected in a suitable well-known manner, (not shown) with an armature coil I0 rotatably mounted in the field of a magnet ll, so that when the cell 9 is activated a by light from the view toward which the camera is directed, the current set up in the armature ID will cause an indicating member or pointer l2, mounted on its shaft to move over a suitable plate I3 of transparent or translucent material, which may be calibrated with a scale or a series of figures l4 representing P values of the lens diaphragm or shutter speed settings according to the usual standards. The action of light of greater intensity, in the present instance, causes the indicator or pointer l2- to move toward the right as viewed by the operator.

The camera is shown as provided with a well known type of direct view finder, built into the carrying handle IS, the eyepiece frame IS with its lens or peepsight l1 being at the rear, and the object glass l8, having a carrier l9 that is pivoted at 20 to projections 2| on the housing 5, being in the front end of the handle. I

In an opening 22 in the rear of the housing I, and under the finder glass I8, is mounted an optical member 23, which may be a prism, for bringing the pointer l2 and its scale ll into the field of vision of the operator through a slit 24 in the eye-piece frame It. The scale It somewhat magnified, is visible by light that enters anopening 6 simultaneously with the view in the finder, without requiring awkward effort by the operator.

In front of the scale plate II is another hand or pointer 2i, pivoted at 20 approximately coaxially with indicator II, but not in any way connected to the latter or to the other parts that are light-actuated. The manner of mounting the pointer 2| is not illustrated in detail, but its pivot 20 may be on a bracket at the bottom of housing I, and a spring, (not shown) may be provided to bias the pointer 25 toward .one side of the housing I. An arm 21 below the pivot 26 constitutes an extension of pointer 25 and bears on a cam 2| integral with the diaphragm adjusting ring II on the lens mount 2', the ring 29 also carries a knurled lug 30 located at a point convenient to the operator. Movement of this lug ll upwardly or downwardly to adjust the diaphragm D moves the pointer 25 across the scale II and opens or closes the diaphragm D in accordance with the f values corresponding to the position of the pointer on the scale.

In using a camera equipped as illustrated the operator sights through the direct view finder and when the desired view is framed therein, the light value of the scene or object will activate the cell I and the armature I0, so that the indicator I! immediately moves to a position on the scale that corresponds to the correct diaphragm aperture for that particular light condition. The operator then may move the lug 30 by using the thumb or a finger of the same hand that holds the front of the camera, until the pointer 25 coincides with the indicator II, the former being visible through the translucent scale glass i3 and the indicator I! being directly visible between the operator and the scale through the prism 23.

Both pointers are readily viewed by the operator through slit 24 and eyepiece glass l1 simul- 'taneously with the scene framed in the finder glass II. The operator does not have to remove his eye from the finder, but may move the camera from one scene to another, following with the pointer 2| the changes of the indicator II by moving the lug II .and thus constantly correcting the diaphragm opening to suit the existing conditions.

Ifafilmofslowerspeedistobeused,amask may be provided to slip over the front of housing I, thus reducing the total amount of light that reaches the cell I. and necessitating a larger diaphragm aperture for a given condition l'br long distance or telephoto work, the regular lens may be removed and a telescopic type substituted. A detachable fastening may be used, and such fastening is not illustrated in detail. Preferably it may be of the bayonet lock type, so that when the lens mount 1 is turned in its socket to the holding position, a catch such as a sliding bolt Ii movable laterally in an extension 8! of the lens mount, may engage a part on the ofthelineofvision. Tothisendasub-frame I! in which the object glass I8 is mounted, is pivoted at I! in the top of the carrier II, and a friction catch l8 permits the glass II to be swung upwardly to the position indicated in broken lines in Fig. 4. The eyepiece lens I! also is arranged to slide downwardly, knobs 33 guided in slots 34 being provided on either side of the eyepiece frame it for this purpose. Therefore for a close-up" of a distant view the scene is observed through two sight openings without lenses.

It should be pointed out that when the eyepiece lens I! is lowered'for telephoto use, it remains in front of the slit 24 to continue performing its function of enabling the operator to focus on the pointers i2 and 25 and their scale I.

Each telephoto objective as well as the normal objective used on the camera will be provided with a cam 28 having a configuration correlated to its focal length so that adjustment of its diaphragm until the two pointers i2 and 25 are superposed will result in the proper diaphragm setting. With a single fixed scale I the actual f. value of the diaphragm opening may be indicated for only one focallength objective but this is generally unimportant although other scales -may be provided, if desired, for each objective to be used.

Although I have described my invention as embodied in a motion picture camera, it will be obvious to those skilled in this art that many modifications will suggest themselves without departing from the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a motion picture camera, a casing, a virtual image view finder mounted on top of the casing, an objective mount removably mounted on the front of the casing, said mount having a diaphragm and a member for adjusting the diaphragm, a, self contained housing built into the top-front part of the casing, a light sensitive cell and a meter member mounted in said housing, a movably mountedpointer extending into said housing and having a cam lever at its lower end, a cam carried by the diaphragm adjusting member of said objective mount for engaging the cam lever, whereby adjustment of the diaphragm moves said pointer a distance which is a function of the shape of said cam. the shape of said cam being so correlated to the focal length of the objective in said mount that adjustment of the diaphragm to bring said pointer to a position indicated by said meter member results in a proper setting of the diaphragm.

2. An objective mount adapted to be detachably secured to a camera having a photoelectric exposure meter and a pointer movable to a position indicated by the meter to insure correct exposure, said mount comprising an objective lens, a diaphragm, a member movable to adjust the diaphragm, a cam carried by the mount and movable with said movable member, said cam having a configuration corresponding to the focal length of the objective lens and so positioned on said mount that it comes into actuating engagement with said pointer when the objective mount is secured to the camera, whereby adjustment of the diaphragm will move said pointer in accordance with the focal length of the objective lens.

JOSEPH MIHALYI. 

